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Abstract:

A method and container for developing seedlings includes germinating the
seeds and air pruning the seedlings to a depth of about 3 inches.

Claims:

1. A container for facilitating air root pruning of seedlings, h
container comprising: a first dimension of the carton is 3 9/16inches; a
second dimension of the carton is 3 9/16inches; a height dimension of the
carton is 3 to 51/2 inches; and a bottom of the container being an open
bottom, adapted to be set on a mesh support.

2. A method of improving the root structure of seedlings, the method
comprising: placing seeds on a surface of a soil-less growing medium for
germination to obtain the seedlings; subjecting the seedlings to a first
air root pruning by growing the seedlings in a bottomless container of 3
to 41/4 inches deep; and subjecting the seedlings to a second air root
pruning by growing the seedlings in a bottomless container of 3 to 51/2
inches deep.

3. A growing medium for facilitating the development of seedlings, the
growing medium comprising 35% to 40% composted rice hulls, 35% to 40%
pine bark, and sand; and the growing medium comprising a soil-less
seeding medium for placement in containers over a bottomless mesh seed
flat for permitting shallow air pruning of roots, wherein tree seeds are
placed on the growing medium for germination.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS IONS

[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/568,056, filed Aug. 6, 2012, which is a
divisional of U.S. patent application Ser. No. 11/731,997, filed on Apr.
2, 2007, now U.S. Pat. No. 8,236,322, and which is a divisional of Ser.
No. 10/216,092, filed Aug. 9, 2002, now U.S. Pat. No. 7,308,775, and
which claims priority from U.S. provisional patent application No.
60/312,593, filed Aug. 15, 2001, all of which is incorporated herein by
reference in its entirely for all purposes.

BACKGROUND OF THE INVENTION

Field of the Invention

[0002] There is an ever-increasing demand for native hardwoods, but
commercial farming of this class of trees is frustrated by the slow
growth of this class of trees and the difficulty in transplanting them.
Similarly, non-commercial reforestation with hardwoods is frustrated by
the slow growth and transplantation difficulties. "Traditional"
production methods for native hardwoods such as Oaks, Hickories, Ash, Nut
trees and others are notoriously slow growing and tend to develop a
coarse, carrot-like dominant tap root which makes them very difficult to
transplant both in the nursery and especially in out-planting
situations--where mortality rates often ran as high as 70 percent or
more.

[0003] To try and overcome the problems associated with transplantability
of native hardwoods and other difficult to transplant species, many
nurseries began to "root-prune" their plants while in the field one to
three years prior to sale in hopes of developing a "secondary" root
system which would give this class of plants a better chance of surviving
the out-planting process. The major problem associated with root-pruning
in the field is that it not only "shocks" the plants because its root
system has been severed but also halts growth and forces the grower to
"wait" for another year or more for the root system to re-develop.
Although the process of root pruning in the field greatly helped to
minimize loss after out-planting, the process was slow, costly and
extended the time a plant must remain in the nursery.

[0004] One prior art method of root pruning is disclosed in Huang and
Liang, Effects of Air-Pruning on Cutting and Seeding Growth in Container
Tree Propagation, SNA Research Conference 1987, incorporated herein by
reference, pages 134-137.

SUMMARY OF THE INVENTION

[0005] This inventions relates to a method of accelerating the growth and
development of trees via an enhanced root system. Generally, the method
of this invention comprises: Selecting seed of the species to be grown
from trees from the same climate, and preferably the same growing
conditions. Sorting the seed is based upon density, size, and/or weight.
Placing the seed on the surface of a growing medium. Subjecting the seed
to cold stratification in sufficient time to maximize the growing season
(time of last frost to time of first frost) upon subsequent transfer
outside. Transferring the cold-stratified seed to a greenhouse to being
germination is about 30 days, subjecting the seedling to air root pruning
at a depth of about 3 inches. Sorting the seedling according to height
and caliper, and transplanting the seedling to bottomless bands/pots.
Growing the seedling in bottomless bands while subjecting the seedling to
a further air root pruning at a depth of about 41/4 inches. Hardening of
the seedling off, and transplanting the seedling for further growth
outside as close to the beginning of the growing season as possible to
maximize the growing season and growth potential.

[0006] The general method of this invention, without the specific details
of the invention described and claimed herein, is disclosed in Lovelace,
The Root Production Method (RPM) System for Producing Container Trees,
The International Plant Propagators' Society Combined Proceedings, Vol.
48 (1998), incorporated herein by reference.

BRIEF DESCRIPTION OF THE FIGURES

[0007] FIG. 1 is a photograph illustrating the grading of seed by density
using a Jesse Aspirator.

[0008] FIG. 2 is a photograph illustrating the grading of seed by weight
and size using a Savage Sizer and an Oliver Gravity Table for smaller
seed.

[0037] FIG. 31 is a photograph of pecan seedlings new system of air
pruning at 3 in. depth on left showing better growth at time of selection
and grading;

[0038] FIG. 32 is a photograph showing the difference between air root
pruning at 2 inches (left) versus at 3 inches (right);

[0039] FIG. 33 is a photograph of Pecans seeded in an air pruning fiat;

[0040] FIG. 34 is a photograph of European Ash root 160 days from planting
grown in accordance with the principles of this invention;

[0041] FIG. 35 is a photograph of European Ash root 160 days from planting
grown with conventional method;

[0042] FIG. 36 is a photograph of the root system of two or three year old
Pecan grown with convention methods;

[0043] FIG. 37 is a photograph of two air pruned 75 day old Pecan grown in
accordance with the principles of this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0044] The method of the present invention involves consideration of seed
selection, including seed origin (provenance, density, and size). It
further involves consideration of seed handling including stratification,
timing of germination to extend growing season, technique (depth) of
seeding. It further involves air pruning, preferably in two steps using
air as a means of root pruning to enhance the development of a dense
fibrous root mass. It further involves gradation for uniformity of stock
and to reduce transplanting losses. Lastly, the method involves selection
of growing media, including fertilizer, consideration of air space,
wetting agents, and components. The method of the present invention
accelerates rate of growth, and induces early flowering and fruiting.

[0045] Seed selection is an important component in the acceleration of
tree growth. Special attention is provided to assure seed is selected
from superior individual parents, showing outstanding phenotype, typical
of the particular specie or variety of tree. Attention also must be
focused on the climate zone of origin, including attitude and locations
within its native geographical range, normally referred to as
"provenance". Within a given provenance, seed is selected based on
environmental conditions of the final location. It is desirable to select
seed from the same species growing in the same environmental conditions,
e.g., a flood plain or an upland site. Seed is collected site specific.
These different types of seed are referred to as ecotypes. Proper
selection results in tree improvement, superior adaption to planting
sites all of which add to economic and aesthetic value.

[0046] Seed handling is also an important component in the acceleration of
tree growth. Collected seed are processed by cleaning out any foreign
materials. They are then processed through an aspirator to separate out
the heaviest individual seed. Density is the most important factor in
germination capacity of any seed, and survival of the seedling. Density
is a measure of the stored food reserve. After the heaviest seed are
selected they are then processed through a sieve which grades them by
size, e.g. three (3) or four (4) different sizes. Only the largest,
heaviest seed are used. Since these factors (weight, size, and density)
are genetic in nature these processes have definite effects on the
genetic improvement of the progeny.

[0047] Seed stratification and timing are also important in the
acceleration of tree growth. The length of time required for
stratification is predetermined so germination can start (For example
February 1st.) Thus the seed must be handled in such a manor that all
stratification requirements are satisfied prior to February 1st. Thus,
for example, a seed requiring ninety (90) days of cold stratification
would have to be placed in our cold storage November 1st, so that it
could be germinated by February 1st. As shown in FIGS. 5 and 6, the seed
is preferably pre-sown in the stratification media (which is preferably
the same as growing medium, described below) and as shown in FIGS. 7, 8
and 9, the seeded trays are stacked in a cold storage room where
temperature is maintained at 32° F. The seed are placed on the
surface of the growing medium. When germination begins, the outer seed
coat splits exposing the seed cotyledons. When exposed to light the
cotyledons turn from their normal pure white to green, indicating they
are photosynthesizing and producing additional energy for the germinating
seedling. The inventors' research shows that most of the energy produced
by the seed's cotyledons goes to the production of the plants root
system, thus adding to the primary goal of producing and enhancing an
improved root system. This is in contrast to the established conventional
rule that the depth of seed planting should be twice the diameter of the
seed. The 32 temperature will prevent pre-germination of seed once its
ripening requirements have been satisfied. This 32° F. temperature
is also in contrast to the established convention wisdom of temperatures
between about 37° F. to 41° F. Still another difference
from conventional methods is placing the seeds in growing media.
Historically seeds have been stratified separately and then seeded
immediately prior to germinating.

[0048] The timing of the above steps in the method is based on having the
seedlings processed through termination, Step I root pruning, grading,
and Step II transplanting, so they are ready for planting outdoors by the
frost free date (approximately May 10 in Missouri). This gives the
seedlings the maximum growing period until the first fall frost,
approximately 210 growing days. A time sequence might be: February
1st--start germination in greenhouse at a temperature of between
68° F. and 72° F. for about thirty days, as shown in FIG.
10. March 1st transplant to square deep bottomless containers for
additional air pruning of the lateral roots produced in the seed flat
pruning. Containers 23/4×23/4×3 inch have been used
satisfactorily for this step, but the inventors have determined that
containers 3 9/16×3 9/16×41/4 inch produce superior plants as
shown in FIG. 30. At the end of Step II, the seedlings are between 12
inches and 18 inches in height and are ready to be planted in their final
growing container outside in a nursery production area.

[0049] As described above, the seeding is done by placing seed on a
bottomless mesh seed flat. While seed flats measuring 181/2
inches×141/2 inches×21/2 inches deep with mesh spacing of 3/8
inches have been used satisfactorily, as shown in FIG. 29, seed flats
measuring 153/4 inches×153/4 inches×5 inches deep with mesh
spacing of 3/8 inches (FIG. 4) have been found to be optimum. A soil-less
seeding medium and growing medium is preferably used. The seeding medium
consists of 40% composted rice hulls, 40% pine bark, 20% sand, which
results in a desirable 35% air space has been used satisfactorily, but a
medium of 35% composted rice hulls, 35% pine bark, 20% sand, and 10%
manure, which results in a desirable 35% air space has been found to be
optimum. A complete slow release fertilizer plus micro-nutrients and a
wetting agent are added to the medium. The growing medium is also
inoculated with mycorrhizae spores which germinate and grow on and inside
the tree roots in a symbiotic relationship (see FIG. 23). Research has
proven these fungi play an extremely important function on trees. They
provide an immune system for the trees, blocking infectious diseases.
They form such a dense mass they are able to enhance the capability of
the root surface up to 1,000 times further enhancing the uptake of
moisture, nutrients, and air resulting in a plant that can withstand
greater stress situations and still perform and grow, displaying
exceptional vigor.

[0050] There is a universal problem of proper nutrient uptake by woody
plants in artificial (soil-less) growing media. Through analysis of the
media compared to the analysis of the leaves from plants grown in media
for Quercus bicolor--Swamp White Oak, the inventors have determined that
the addition of 10% composted manure to the growing media of composted
rice hulls, pine bark, and sand plus slow release fertilizer and minor
trace nutrient improves the nutrient level in the plants, with most of
the nutrients moving from a low interpretation in the soil medium to a
desired level within the plant resulting in maximum plant growth and
performance.

[0051] The addition of manure promotes the development of a balanced
biological atmosphere within the growing media, promoting the growth of
numerous beneficial organisms. These organisms help promote the
development of desirable soil fauna that break down organic matter
releasing essential bi-products (enzymes etc.) that benefit the plant by
enabling uptake of nutrients that are present in the media here-to-fore
but not available in a form the plant can absorb. This resulted in a
reduced fertilizer rate of 50%, resulting in substantial cost savings.
Also there is less impact on the environment because of fewer nutrients
leaching and run off while still achieving maximum plant growth.

[0052] The inventors have also discovered that the incorporation of 3/4 of
a pound of Talstar systemic insecticide in each cubic yard of growing
media trans locates throughout the plants system, helps plants grown in
the media to ward off attack by a number of undesirable insect pests
including but not limited to Japanese beetle.

[0053] As shown in FIGS. 10 and 11, in the first air-pruning step, seeded
flats are placed on raised greenhouse benches with air circulating
beneath the benches. As germination of the seed begins to occur in the
above-described bottomless flat, the following sequence occurs. The
seedling radical (tap root) penetrates down through the media and emerges
through the 3/8 inch mesh, coming into contact with air circulating
beneath the raised bench (see FIG. 12). The root tip is killed (dried) by
the air, at a depth of 3 inches. Compare FIG. 37, showing a
conventionally grown pecan seedling, with FIG. 36 showing a pecan
seedling grown in accordance with the principles of the present
invention. The shallow air pruning achieved with the method of the
present invention induces rapid lateral root development high (where most
desired) on the tree root collar where their function to the welfare of
the tree will be best served.

[0054] This root pruning preferably occurs at about 21/2-3 inches.
Extensive research conducted by the inventors has established that the
ideal depth for the first air root pruning (FIGS. 31 and 32) is about 3
inches.

[0055] As shown in FIG. 30, in the second air-pruning step, graded
seedlings are transplanted into a bottomless band measuring 3
9/16×3 9/16×41/4 inches. This size band has been found to
give improved growth and improves the root distribution in the production
container. The Step II transplanted seedling bottomless bands are placed
on raised bottomless benches to promote additional air pruning, which
occurs on secondary lateral roots further enhancing the development of a
shallow dense root mass with many root tips. The first two steps are
timed so the bands are ready to be transplanted outside in the container
production area during early May to avoid late frosts, but timed to take
advantage of a full growing season. Timing is further important because
if properly handled it can coincide with the tree setting a temporary
terminal bud. When this occurs, photosynthate is trans located from the
leaves down to the roots. This promotes very active root development,
thus quick establishment in the container area resulting in accelerated
growth.

[0056] The inventors' research also determined that the optimum size of
the container for Step II is a bottomless tree band measuring 3
9/16inches×3 9/16inches×41/4 inches deep (see FIG. 30)
produces the ideal root mass to top (all of plant above soil) ratio.

[0057] This shallow air pruning is unique to the method of this invention,
and enhances the root system resulting in the production of a superior
plant that can survive, perform, and grow faster under every condition
tested. Prior root pruning methods typically prune at least 5 inches or
more. The shallower air pruning of the present invention induces rapid
lateral root development high on the tree root collar, where most
desirable, and where their function to the welfare of the tree will be
best served.

[0058] The inventors have also tested various bench heights (i.e., the
height from the greenhouse floor to the wire mesh supports) under a
strictly controlled greenhouse environment, for both the first and second
air root pruning steps. Heights of 12, 18, 24, 30, and 36 inches were all
carefully tested. While there was little differences in the 30 and 36
inches bench heights, both were far superior in air flow and subsequent
root pruning to 12, 18, and 24 inches. As a result, the inventors have
determined that balancing effectiveness of root pruning versus
construction and installation costs, and ergonomic considerations, a
height of 30 inches is optimum.

[0059] The seedlings are graded to identify the genetically superior
individuals. Experience and research has proven that selecting the
largest seedlings after their first flush of growth identifies those
individuals that will remain dominant, grow faster, and exhibit genetic
superiority when grown to a larger size and eventually out planted. When
grading, particular attention is given to the combination of height,
caliper, and root development. On most species of woody plants the top
50% are retained and transplanted and the remaining plants are discarded.
This grading process has proven to be a significant step in tree
improvement.

[0060] The graded seedlings are then transplanted into a bottomless band
measuring 27/8''×27/8''×33/4'' in depth. (This short band
gives improved growth and improves the root distribution in the
production container.) The transplanted seedlings in the bottomless bands
are placed on raised bottomless benches to promote additional air
pruning, which occurs on secondary lateral roots further enhancing the
development of a shallow dense root mass with many root tips. The first
two steps are timed so the plants are ready to be transplanted outside in
the container production area immediately after the last frost date
(early May in Missouri) to avoid late frosts, but timed to maximize the
growing season. It is also desirable to coordinate transplantation
outside with the tree's setting a temporary terminal bud. When this
occurs, photosynthate is trans-located from the leaves down to the roots.
This promotes very active root development, and thus quick establishment
in the container resulting in accelerated growth.

[0061] As shown in FIG. 16, while in the greenhouse, the bands are
preferably contained in bottomless flats each holding 25 tree bands. When
preparing to transplant out of doors plants must be handled in a special
manner to make the proper transition from a controlled greenhouse
environment to a more stressful outdoor environment. The greenhouse
process conditions the stomata (openings on the underside of the leaf) to
lose their elasticity and they are unable to narrow or close and control
transpiration (water loss) and the cuticle, a waxy layer that forms on
the leaf surface and protects the leaves has not formed. Both of these
conditions correct themselves in 48 hours when placed outdoors in full
sunlight. During this period they are intermittently misted to relieve
stress while becoming acclimated. After becoming acclimated they are
moved to a container production area (see FIG. 20), and transplanted into
existing pre-filled containers (see FIG. 19). A shallow wide growing
container is used, because most of the feeder roots remain in the upper
six to eight inches of soil after out-planting. The growing container
measures 10 inches across and 7 inches deep (see FIG. 19). This allows
25% more lateral root development than a smaller size previously used.
This production system results in growth to a marketable size in one
growing season of approximately 210 days from date of seed germination
(see FIG. 21).

[0062] As shown in FIG. 22, the root mass achieved with the methods of the
present invention eliminates losses often experienced using
conventionally grown trees, especially those recognized to be difficult
to transplant, such as Oak, Hickories, Ash, and Nut Trees. Using the
methods of this invention, the inventors have achieved consistent
survival rates greater than 95%, even at very stressful sites such as
wetlands, (where flooding occurs), mine reclamation sites, and
construction sites.

[0063] The trees produced with the method of this invention grow an
average of three times faster than conventionally grown seedlings. As
show in FIGS. 24, 25, and 26, even after 15 years, the trees grow at 3
times the rate of conventionally produced trees. This accelerated growth
rate greatly increases the value and economics of tree farming. Using the
methods of this invention, the rate of turnover in most tree production
could be increased by 50% or more and make tree farming a profitable and
viable growing enterprise.

[0064] Most varieties of trees grown under this production system have
exhibited early flowering and fruiting characteristics. Examples are
Swamp White Oak (Quercus bicolor) and Bur Oak (Quercus macrocarpa). It is
generally accepted in the literature that these species begin flowering
and fruiting at about 20 to 25 years of age. See, Schopmeyer, Seeds of
Wood Plants in the United States, Agriculture Handbook No. 450, Forest
Service, U.S. Department of Agriculture, Washington, D.C., Table 2
(1974), incorporated herein by reference. However, as shown in. FIGS. 27
and 28 trees of these species grown in accordance with the methods of the
present invention have consistently produced fruit in the 3rd year after
out-planting. The inventors believe that these plants have as many root
tips (where the hormones are produced) as naturally grown 20 to 25 year
old trees. This fast fruiting is very valuable from a regeneration and
wildlife food standpoint. The inventors' research indicates this same
response occurs in both nut trees and fruit trees, specifically pecans,
walnuts and apples.

[0065] Specific differences between the method of the present invention,
and prior methods of tree production include: (1) the shallow depth of
air pruning (about 21/2''); (2) seed grading to select genetically
superior seeds; (3) transplantation after the first root pruning to
bottomless bands to further increase root mass, as shown in FIGS. 16, 17,
and 28; (4) the shallow depth of the bottomless band compared to
conventional deeper containers that accommodated the tap roots 3
9/16inches×3 9/16inches×41/4 inches; (5) the growing medium
(see FIG. 19) that combines the proper amounts of air, nutrients, and
beneficial natural soil born organisms in balance with an enhanced root
system that properly utilizes and assimilates them, the result is greatly
accelerated growth rates that persists for years; (6) high
transplantability and survival of trees produced with the method of this
invention, which is nearly 100% survival when out-planted under virtually
all conditions, and greater than 95% plus on stressed sites where
conventional produced seedlings survived at rates of 2% or less. Sites
tested include wetlands that are repeatedly flooded, strip mine
reclamation, and other problem planting sites and conditions.

[0066] The inventors have propagated approximately 750,000 containerized
oak and nut tree seedlings per year, many of which have been out-planted
on abandoned mine lands, old wetland sites and fields in central and
western Missouri. First-year establishment success for containerized
seedlings is approximately twice the success of bare-root seedlings in
side-by-side field trials. Greatest mortality resulted from excessive
competing vegetation and rodent damage in winter. Tap-rooted hardwoods
such as oak, hickory, and walnut responded well to air-pruning, which
resulted from using bottomless containers. Seedlings were propagated and
placed upon a raised, welded hog or cattle panel, with four-inch squares,
protected from squirrels by a wood frame and chicken wire.

[0067] Qualitative observation of establishment success suggests a
first-season survival rate of 90 percent for air-pruned bur oak and pecan
grown in half-gallon bottomless containers. This compares to 40 to 50
percent survival of year old bare-root stock grown at a local nursery.
These were side-by-side trials of seedlings planted in prepared rows of
prairie soils in Conservation Reserve Program (CRP) crop fields in
western Missouri. Rows were set at 15-foot centers, disked, and planted
by hand. Containerized seedlings were planted in fall, and bare-root
seedlings were planted in spring. Success rates were slightly higher in
very fine sandy loam soils mapped as Bates loam, (2 to 5 percent slopes,
fine-loamy, siliceous, therrvic (Typic Argiudolls) compared to silty clay
soils mapped as Kenoma (2 to 5 percent slopes, fine, montmorillinitic,
thermic Vertic Argiudolls) (USDA 1995). Competition became intense in
mid-summer as late-season weeds such as common and giant ragweed;
cocklebur and begger ticks germinated from the old-field seedbank. The
rows were mowed in July to prevent shading of the seedlings.

[0068] A second test plot was established on rough-graded, neutral mine
spoils (silty clay texture with 15 percent shale charmers, 5 percent
sandstone pebbles and few sandstone cobbles) in western Missouri.
Establishment success in the first season was approximately 75 percent
for containerized bur oak and pecan compared to 30 percent for bare-root
seedlings. Compaction was minimal since all grading was performed by a
D-3 dozer knocking the tops off the spoil-ridges, pushing the fill into
the valleys between ridges. Wind-disseminated species, particularly
broomsedge, slowly colonized the plots, competing with the seedlings.
Adjacent mine spoils were heavily vegetated, enabling deer to browse the
plot undisturbed.

[0069] A third test plot was established in central Missouri on
loess-derived forest soils that had been cleared in the 19th century,
farmed and planted to tall fescue in recent decades. In places, much of
the A horizon had been eroded and mixed by plowing into the E horizon.
The soils were classified as eroded Winfield silt roam (fine-silty mixed
mesic. Typic Hapludalfs) (USDA 1994). Fescue sod was removed with a heavy
hoe around each seedling to reduce competition at the time of
establishment. Spraying also is effective; but the seedlings should be
dormant. First-year success rates for containerized bur and northern red
oak were 90 percent compared to 25 percent for bare-root.

[0070] The following table shows a hypothetical cost/benefit analysis of
plants grown in accordance with the principles of the present invention
versus conventional bare root plants,